I want to upgrade our Avante Price Pfister series 09 tub/shower trim and have committed to finding out if it's reasonable. Given the location of our valve our plumber strongly advised we upgrade the valve rather than replace it and we agree. This means we will install a retrofit kit so the old valve can be used with newer trim and Price Pfister told me which trims will work with the retrofitted valve. Now my question:

The picture below is the hole in the wall for the old trim with the valve behind it. The hole is 6 1/4" wide and 3 3/4" high. The surface in the picture is cultured marble. I should mention that there is no back access. The PP model that I think may work is the Avalon R89-8CBC.

The specs say the trim flange is 6.88". But there is no information about the size of the gasket flange (see picture below) so I don't know if I have enough leeway there for the gasket flange. Is there a standard thickness for the gasket flange. I need to make sure it is on the surface and not in the hole.

The instructions for the Avalon series indicate a hole of 4 3/4â€ Dia. or 4â€ Dia. for Thin
Wall Installation (Picture below).
1. I assume this means we have to make the height of the opening larger. Is this so? And does anyone know if cutting cultured marble is difficult and/or expensive?
2. What is Thin Wall Installation? Can you tell if that applies here?

If we proceed with this, we'll have a plumber do the work. What I need to know is if it is possible (that is the new trim would fit) and if it is reasonable (that is to cut the marble, if necessary). If it is, then I'll figure out about enlarging the opening, buy the trim, and call the plumber

Thank you for your response. With all the other work we're doing, I decided that this work, if it becomes really necessary, can be accomplished later. I am going to leave the valve and original plate and probably replace the shower head and spout, which are the major problems now. Perhaps there will be new escutcheon or flange shapes and sizes in the future.

I did find a remodel cover plate and valve that is not as common but is a little more attractive (to me at least). It's a Symmons D-86-2-OP-LR. It is oval and still quite large 13" x 85/16", which is the idea for a remodel plate but kind of big for our little bath. I mention it in case it is of use to you to know about it. There are a number of options in the OP series and they all include the remodel plate.

So now it's on to other problems and I will revisit this down the road.